A linear log-MAP algorithm for turbo decoding and turbo equalization

A simplification of the log-MAP algorithm for use in turbo decoders and turbo equalizers is presented. The simplified algorithm is based on the MacLaurin series expansion of the logarithmic term in the Jacobian logarithmic function used in the log-MAP algorithm. In terms of complexity the proposed algorithm can easily be implemented using adders and comparators as this is the case for the max-log-MAP algorithm. Also, simulation results show that the proposed algorithm has performance very close to the log-MAP algorithm for both turbo decoding and turbo equalization, even in a high loss intersymbol interference (ISI) channel where there is a wide gap between the performance of the log-MAP and max log-MAP turbo equalizers.